Kidde CO and Smoke Alarm Value Pack: * CO2 alarm uses 3 AA batteries (included) * Smoke alarm uses one 9V carbon zinc battery * Included CO Alarm snap open cover gives immediate access to batteries * Smoke alarm hush feature * Kidde smoke alarms and carbon monoxide detectors meet the requirements of Underwriters Laboratories (UL), an independent facility that tests products for compliance with widely-accepted safety standards